Method of and a mold and ingate system for casting metals



March 1963 P. F. SUNDIN 3, 8

METHOD OF, AND A MOLD AND INGATE SYSTEM FOR CASTING METALS Filed March 4, 1960 'i INVENTOR.

PER Freeoram Sumnm bs wwwm.

ATTYS,

States The present invention relates to a method of, and to cores and molds for casting metals, such as iron, steel, copper and other metals. The object of the invention is to provide a method of casting metals, and to provide mold and core parts made from an inexpensive material, which provide several important advantages as will appear hereinafter, taken in connection with the accompanying drawing wherein:

FIG. 1 is a vertical cross section through a mold showing an ingate system with a strainer core, and

FIG. 2 is a sectional view taken substantially in the plane of line 33 on FIG. 1.

In accordance with this invention, this and other objects are achieved by making molds and cores for metal casting at least in part from sponge iron.

Sponge iron, the normal use of which is as a substitute for scrap-iron as a raw material in the production of high-quality steel in open-hearth and electric furnaces, is a product obtained by reduction of iron ore at so low temperatures (900-1100 C.) that neither the ore nor the iron melts, but the iron is partially fused, as it is reduced, so as to form a spongy product of high porosity. Sponge iron is to be distinguished from ordinary sintered metals prepared by compression of a metal powder under high pressure and at a high temperature. Such sintered metals have some porosity, but this is much lower than that of sponge iron wherein the porosity is so high that the product is very light (bulk density usually about 2) and is highly gas-permeable.

Sponge iron generally has a high content of iron, which may vary between 90 and 99% by weight, the remainder being mainly unreduced ore and slag. .The contents of carbon, phosphorus and sulfur are very low.

In one method of making sponge iron, the so-called Hogan'zis method, a highly-enriched iron ore concentrate, containing about 70% Fe, is reduced with coal or coke as the reducing agent. The ore concentrate and the reducing agent are placed in alternating layers in refractory crucibles, limestone being added to bind the sulfur of the fuel. The crucibles are heated in a furnace at about 1100 C. for many hours whereby the ore is reduced. The sponge iron is normally obtained as fiat cakes or as big pipes. Sponge iron produced by this method is very pure (9699% Fe), uniform and gas-permeable and is therefore excellently suitable for use in the present invention. However, other methods of making sponge iron are known and practiced and sponge irons produced by such methods can also be used in accordance with the present invention with satisfactory results.

The use of sponge iron for the manufacture of molds and cores in accordance with the present invention has many advantages. Sponge iron is sufficiently refractory and has good mechanical strength properties at high temperatures. It is an inexpensive product which is readily available in great quantities and is easily worked and welded so that the manufacture of mold and core parts of desired shape is simple. In this connection it is to be noted that it is possible to prepare sponge iron pieces of a desired shape by imparting the desired shape to the iron ore before it is reduced so that it is possible to make pieces which can be used as mold or core parts directly or with aren't ICC a minimum of working. It will be noted that it is possible to obtain by this method at very low costs shapes which could not be obtained at all or obtained only at great costs by sintering metal powder. It is further to be observed that in contrast to most molds and cores made from conventional materials, such as sand with or without binders, the parts made from sponge iron can be used several times (reusable or semi-permanent cores and molds) which means that the cost will be very small as compared to, e. g., sand mold and core parts. When the sponge iron part is finally scrapped it still has some value as an iron material and is charged to the cupola or other melting furnace.

The high gas-permeability of sponge iron facilitates the removal of gases from the cast metal and from other parts of the mold. The sponge iron part can further be made hollow which further facilitates the removal of gases. Furthermore, the cooling of those portions of the castings which are in contact with sponge iron parts is improved as compared to core or mold sand which results in a more favourable structure in such portions of the casting. The chilling action can be improved by passing a cooling medium such as air or water, through the sponge iron in the mold. The same result may be achieved erg. by soaking the sponge iron part in water before it is positioned in the mold.

The sponge iron may be used in various ways in molds and cores. In the case of a mold or core member of complex configuration, a sponge iron member of simple form, such as a cylinder or a cone or the like, may be used as a frame or skeleton upon which the desired mold or core part is built up from a layer of sand or the like, containing a binding agent, in the desired complex shape. The sand layer may be only as thick as necessary to achieve this configuration. In one method of making such mold or core members, the sponge iron part may be positioned in a core box or similar means of the requisite configuration and a sand mix containing a binder may be blown through passages provided in the sponge iron into the clearance between the core box or the like and the sponge iron. The binder may then be hardened in any suitable manner. The sand mix may contain e.g. water glass which may be hardened with carbon dioxide, which can then be blown through the sponge iron. The binder may also be a synthetic resin which can be hardened by treatment with heat (for example a heated core box) or chemical agents. Molds and cores of very smooth surface structure can be prepared in this way.

The sponge iron can also be used in such a manner that it LfOIl'IlS at least portions of the walls defining the mold cavity, e.-g. to achieve an improved cooling of certain surface areas of the casting. In order to prevent the sponge iron from adhering to the casting it is in such a case as a rule necessary to apply a thin coating (black) which separates the sponge iron from the casting. Such a coating can consist of a particulate refractory material, e.g. silicon carbide, sand, graphite, Zirconia, kieselguhr, together with a binding agent.

However, in some cases it is not desirable to take steps .to separate the sponge iron mold parts from the castings, but they may remain in the castings after the shake-out. For example, a tube can be cast around a sponge iron core, which can be allowed to remain in the tube, since due to the high permeability of the sponge iron it will not prevent flow of a gas or liquid through the tube. Such a tube can be used with great advantage for example in heat exchangers.

In all types of casting, strainer cores are widely used to control the flow in the ingate system and to separate slag from the metal. The strainer cores are usually ceramic but they can with advantage be made from sponge iron. Sponge iron strainer cores have less cracking tendency, they show higher strength at elevated temperatures, are inexpensive and do not contaminate the scrap. For metals with high melting temperature they should be covered with some coating, for example a thin layer of powdered kieselguhr.

In FIGS. 1 and 2 of the accompanying drawing, 11 and 12 denote, respectively, upper and lower mold parts. In the upper mold part 11 thus formed, there is provided an ingate 13 opening into a sump 14 in the lower mold part from which sump flow passages 15 and 16 lead to the mold cavities (not shown).

In accordance with one aspect of the present invention, and as mentioned above, there is provided a strainer core 17 made from sponge iron and positioned between the lower end of ingate v13 and sump 14. The strainer core 17 is partly supported by the lower mold part 12 as shown in FIG. 2. The illustrative strainer core 17, as shown in FIG. 2 of the accompanying drawing is made as a circular or annular disc having a centrally located hole 18 therethrough.

Strainer cores according to this invention may be made in several shapes, for example, circular, square, rectangular or triangular in plan and of varying thicknesses and may be provided with one or more holes.

The above embodiments are given only to illustrate the invention and are capable of many variations and modifications without departing from the scope of the invention. When the term mold is used in the specification and in the claims, it is intended to cover molds, cores and the like, as will be readily apparent to those skilled in the art.

I claim:

1. A method of casting metals in a mold having an ingate system comprising placing in the mold ingate system a strainer core formed of sponge iron, and casting molten metal into said mold, said strainer core controlling the flow of metal into the mold.

2. The method of claim 1 wherein said strainer core is formed of spong iron obtained by the direct reduction of H011 ore.

3. In a mold and ingate system for metal casting a porous sponge iron strainer core in said ingate system for controlling the flow of metal into the mold.

4. A mold and ingate system as defined in claim 3 wherein said strainer core is formed of sponge iron obtained by the direct reduction of iron ore.

References Cited in the file of this patent UNITED STATES PATENTS 1,592,536 ONeill July 13, 1926 2,028,699 Greene et al Jan. 21, 1936 FOREIGN PATENTS 386,302 Great Britain Apr. 9, 1931 OTHER REFERENCES Jones Powder Metallurgy, pp. 133135, 1943. Journal of Metals, pp. 1440-1444, 1957. W. D. Jones: Principles of Powder Metallurgy, pp. 120- 139, Edward Arnold & 00., 1943.

Metallurgical Dictionary, 1. G. Henderson and I. M. Bates, p. 302, 1953. 

3. IN A MOLD AND INGATE SYSTEM FOR METAL CASTING A POROUS SPONGE IRON STRAINER CORE IN SAID INGATE SYSTEM FOR CONTROLLING THE FLOW OF METAL INTO THE MOLD. 